Photochemical modification of oxide surfaces

Silicon and aluminum, after oxygen, are the most abundant elements on earth. Their oxides are stable, relatively inert and cheap. Because of this, these oxides have found many applications, for example as support material in catalysis or in chemical analysis. Many of these applications require tailoring of the surface properties. The currently prevailing method for surface modification of oxides is based on organosilanes. However, due to the tendency of these molecules to form multilayers, reproducibility remains an issue. Other methods, for example those based on organophosphonates, usually yield monolayers which lack hydrolytic stability. In addition, no method is available that is compatible with (constructive) photolithography.

Goal: The aim of this project was to develop a reproducible method for the organic modification of oxide surfaces that yields hydrolytically stable monolayers and that is compatible with photolithography. This has led to the development of a modification method that is based on the photochemical attachment of 1-alkenes to the oxide surface. Currently, we are investigating the compatibility of functional groups with the newly developed modification method. In addition, the photolithographic patterning of spatially confined systems, such as microchannels, is studied.

Figure 1: Water drop on porous alumina that has been modified with 1-hexadecene (left). Micrograph of a hydrophobically patterned fused silica sample exposed to water vapor (right)